1. Field of the Invention
The present invention relates to a method of storing data relating to the life or history of complicated products. An example of such products are various kinds of automotive vehicles, particularly cars.
2. Description of the Related Art
The kind of device used to this end is a transponder, a registration transmitter or a so-called escort memory. A common feature of all devices of this kind is that they are able to communicate with a so-called registration unit which includes a transmitter/receiver unit. This communication is two-directional, since the registration unit is able to transmit a signal containing information which is received by the transponder and stored therein. Furthermore, the registration unit can transmit a query signal which is reflected by the transponder while the signal is modulated with a signal corresponding to the information found stored in the transponder. By reflection is meant that the transmitted query signal is received by the transponder and re-transmitted without adding new energy to the signal. Registration units and transponders of this kind are known from the Swedish Patent Specification Nos. 7503620-2, which has a corresponding U.S. Pat. No. 4,242,661, to Bengt Henoch and Eilert Berglind, dated Dec. 30, 1980, and 7609732-8, which has a corresponding U.S. Pat. No. 4,390,880, to Bengt Henoch, dated Jun. 28, 1983, among others.
In modern product and service apparatus, it is important that data is continuously collected and stored with respect to the complicated product concerned, and that the correct data is available at the right time for the right product.
This is particularly important in the case of so-called computer assisted and computer integrated manufacture, CAM and CIM, where data feedback relating to complicated products, such as cars, household machines, etc., is essential during the whole of their life cycle.
In automated and computer assisted production lines for complicated products, for example cars, it is normal to use transponders or escort memories fitted to the product, so that different production data is automatically stored on the product.
Such registration transmitter, transponders or escort memories are well known to the art. These units are based on a two-way communication link which utilizes electromagnetic waves in a frequency range of from 100 kHz and up to IR.
Such registration transmitters have properties which are adapted to different applications, with respect to signal range, memory capacity, data speed, etc.
One requirement in the car industry is that the registration transmitter shall be able to pass through varnishing furnaces heated to temperatures of up to 250.degree. C. This requirement is satisfied by providing the registration transmitter with a heat protector, or by supplying the registration transmitter with energy in a cordless fashion from the registration unit and therewith omitting a battery, although the range is much smaller in this case.
When using a registration transmitters or escort memories in a production line, the registration transmitters or escort memories are reused subsequent to having passed through a production line, i.e. are returned to the beginning of the line and fitted to a new product. It is also normal to use different registration transmitters in different sections of a production line.
It is desirable to be able to use one and the same registration transmitter throughout the whole of the production line, and also to allow such a registration transmitter to stay permanently with the product, the car, and therewith provide a function in subsequent service and maintenance of the vehicle. It has not been possible to fulfil these desiderata for several reasons, as will be explained below.
One problem with the use of such registration transmitters or transponders in storing life data relation to a product, such as a car, is that they must be so inexpensive as to render it unnecessary to reuse the same for cost reasons. The actual problem lies in the fact that a transponder which will fulfil requirements during manufacture of the product and which will communicate with a computer in the finished product has hitherto been much too expensive. This drawback is associated, among other things, with the necessary maximum range of information transmission which must necessarily be found in certain sections of the production line, and also the large amount of data which needs to be stored in the transponder in certain stages of manufacture. In order to obtain a sufficiently long range, it is necessary to transmit the information in the form, for instance, of signals of microwave frequency. However, the expense incurred by the use of such techniques is totally unacceptable when the transponder is mounted in the finished product for the purpose of exchanging information with a local computer. Furthermore, the maximum amount of data required in manufacture is greater than what is necessary in the finished product.
These problems are solved by the present invention.
The Swedish Patent Specification No. 8802230-6, which has a PCT International Publication No. WO 89/12935 dated Dec. 28, 1989, teaches an arrangement for the contactless transmission of a serial two-wire data bus, comprising a clock line and a data line connected to a transmitter, a receiver and a demodulator. The transmitter includes an oscillator and a modulator which is intended for modulating the signal generated by the oscillator in response to the signal on the clock line and date line respectively. The invention according to this patent is characterized in that the modulator is constructed to perform two significant, separate modulation steps which do not coincide in time on the signal generated by the oscillator, and consequently two independent signal channels are formed, of which a first is intended to carry data signals and the other to carry clock signals. The demodulator is intended to demodulate a signal which has been modulated by the receiver and received in the aforesaid manner, and is constructed to recreate the aforesaid two signals. The demodulator has a clock-like output and a data-line output.
This patent specification thus teaches a method of separating the data and clock lines, despite using only one signal communication signal with the contactless transmission of data.
The Swedish Patent Specification No. (Patent Application 8902808-8) teaches an advantageous method of enabling in such data buses or other data links the signals transmitted from the master side to be used as guide oscillators on the slave side, and therewith to enable the slave side to transmit signals which are received on the master side without the signals transmitted by the master side disturbing reception of the signals transmitted from the slave side and without the occurrence of zero points, so-called nodes, in the signal arriving from the slave side.
Patent Specification No. (Patent Application 8902808-8), which has a PCT International Publication No. WO 91/03109, dated Mar. 7, 1991, teaches a method of contactless transmission of information between a transmitter/receiver unit and a transponder, this transmitter/receiver unit including oscillators, transmitting and receiving antennas, a modulator and a detection circuit. The transponder includes a transmitter/receiver antenna, a modulator and a detection circuit. The invention is characterized in that the transmitter/receiver unit is caused to transmit a first and a second carrier wave which have different frequencies (f1, f2) but the same phase; in that the difference frequency is formed in the transponder; in that a third signal having the difference frequency (f3) is caused to be divided into a fourth signal having half the difference frequency (f4); in that the fourth signal is caused to modulate the two carrier waves received in the transponder by applying the carrier waves to a diode or the like, so that the received carrier waves are reflected back to the transmitter/receiver unit; in that the signal received in the transmitter/receiver unit is mixed therein with one of the frequencies of the first or the second carrier waves; and in that the two sidebands on respective sides of the carrier wave frequency at which said mixing takes place are produced, these sidebands differing from the last mentioned carrier wave frequency by a frequency which is equal to half the difference frequency (f4), wherein that sideband which has a frequency midway of the carrier wave frequency is a superimposed sideband which is caused to have an amplitude which differs from the amplitude of the other sideband, and wherein the pair of sidebands are filtered out and detected in the detecting circuit of the transmitter/receiver unit with respect to the information content of said sideband pair.
Thus, in combination, these two last mentioned patent specifications teach a method of designing a contactless communication link inexpensively, in that only one communication signal is required and in that the transponder need not include a local oscillator.
Although these patent publications describe techniques which provide an inexpensive transponder, the patent specifications do not disclose how such an inexpensive transponder is able to fulfil the aforesaid requirements, namely that the transponder shall be adapted both to manufacture and also to subsequent use in the product manufactured.